The pine vole is a major hazard to apple trees in the Cumberland--Shenandoah region of the eastern United States, western North Carolina and eastern New York. A recent study in Henderson County, North Carolina, revealed that this animal was the most serious cause of apple tree mortality. Although less damaging because more easily controlled by chemical and cultural means, the meadow vole is also an important hazard to apple growing throughout the eastern United States; see Proceedings of the Fourth Eastern Pine and Meadow Vole Symposium-Feb. 21-22, 1980, where the use of vole-resistant stock systems are discussed.
Wysolmerski et al, J. Amer. Soc. Hort. Sci., 105:675-677 (1980), describe laboratory evolution of Malus cultivars and hybrids for susceptibility to damage from pine voles.
Cummins et al, "Multiple-Stock Apple Trees", Transactions of the Illinois State Horticultural Society and the Illinois Fruit Council - 1976, describe multi-stock apple trees, e.g. trees with distinct rootstocks and interstems, under a fruiting top.
Cummins et al, "Apple Rootstock Problems and Potentials", New York's Food and Life Sciences Bulletin No. 41, May 1974, discuss the use of clonal rootstocks.
Co-pending plant patent application Ser. No. 391,897 filed June 6, 1982 by James N. Cummins, Herb S. Aldwinckle and Ross E. Byers, entitled "Apple Tree" describes a new and distinct apple clone (a seedling of Malus prunifolia) discovered in a test planting belonging to New York State Agricultural Experiment Station, Cornell University, Geneva, Ontario County, New York. This apple clone is the preferred rootstock employed in the trees of this invention. The above-identified application is hereby incorporated by reference.